KR920005263B1 - Optical pick-up device - Google Patents

Abstract

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Description

Pick up device

FIG. 1A is a side view showing an optical path of a laser beam generated by a light emitting element in the optical pickup device of the present invention.

FIG. 1 (b) is a side view which shows the optical path of the light which returns from a disk similarly.

2 is a front view similarly showing an optical path.

3 is a block diagram of a signal detection circuit.

4 is a diagram showing the intensity distribution of the laser beam irradiated onto the disk.

5 is a plan view showing the arrangement of light receiving elements.

6 (a) to 6 (c) are plan views of light receiving elements respectively showing the principle of the knife edge method.

7 is a diagram showing an example of inappropriate arrangement of the light receiving element.

8 is a longitudinal sectional front view of a light emitting device package.

9 is a longitudinal sectional front view showing another example of the light emitting element package.

10 is a perspective view showing the structure of a conventional optical pickup apparatus using a diffractive element.

11 is a block diagram of a signal detection circuit in a conventional optical pickup apparatus using a diffraction element.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an optical pickup apparatus for use in a CD [compact disk] player or an optical video disk apparatus.

In a general optical pickup device used for a CD player or the like, a tracking error signal TE is detected in addition to a main spot for detecting a reproduction information signal RF and a focus error signal FE. In many cases, a three-spot method using two dedicated sub spots is employed.

On the other hand, in recent years, the optical pickup apparatus which can reduce the number of components of an optical system by using a diffraction element (hologram element) is developed. Examples of such a conventional optical pickup apparatus are shown in FIGS. 10 and 11.

In this conventional optical pickup apparatus, as shown in FIG. 10, the laser beam generated by the light emitting element 11 passes through the diffraction element 12 first. The zero-order diffracted light passing through the diffraction element 12 is again focused on the recording surface of the disc 15 with the collimate lens 13 and the objective lens 14 interposed therebetween.

Next, the light returned from the recording surface of the disk 15 again reaches the diffraction element 12 with the objective lens 14 and the collimated memories 13 interposed therebetween.

Incidentally, the diffraction element 12 is divided into regions 12a and 12b having different diffraction directions by the dividing line along the track direction of the disc 15. As shown in FIG.

For this reason, the first-order diffracted light in one region 12a of the diffraction grating 12 is condensed on one of the two light receiving elements 16a. 16b. In addition, the first-order diffracted light in the other region 12b is condensed on the other light-receiving element 16c. 16d similarly divided into two. The output signals Sa-Sd of these light receiving elements 16a-16d are reproduced by the arithmetic circuit shown in FIG. 11, the focus information signal RF, the focus error signal FE, and the tracking error signal. Are converted to (TE) respectively.

That is, the reproduction information signal RF is detected by adding all of the output signals Sa-Sd with the addition circuits 20, 21, and 23 therebetween as follows.

RF = Sa + Sb + Sc + Sd

In addition, the focus error signal FE performs the following calculation on the output signal Sa-Sd with the addition circuits 17 and 18 and the subtraction circuit 19 in between, based on a kind of knife edge method. It detects by doing.

FE = (Sb + Sc)-(Sa + Sd)

Further, the tracking error signal TE is calculated based on the push pull method, and the following calculation is performed on the output signal Sa-Sd with the addition circuits 20 and 21 and the subtraction circuit 22 interposed therebetween. Detection is performed.

TE = (Sc + Sd)-(Sa + Sb)

That is, the luminous flux of the laser beam is divided into two directions by the dividing line along the track direction, and the tracking error signal TE is detected based on the intensity difference.

However, when the optical axis of the objective lens 14 is missed by, for example, a tracking servo or the like, and the optical axis of the objective lens 14 is out of the proper position or tilted, the intensity distribution of the laser beam is distributed. The peak position at deviates from the optical axis.

Deviation from the optical axis center at this peak position affects the intensity difference of the luminous flux of the laser beam divided in two directions.

Therefore, in the conventional optical pickup apparatus which detects the tracking error signal TE by the push-pull method using the diffraction element as described above, an offset is likely to occur in the tracking error signal TE. Therefore, there is a problem that if any deviation occurs in the optical axis of the optical system, accurate tracking control cannot be performed.

The object of the present invention is to reduce the manufacturing cost by reducing the number of parts of the optical system, and furthermore, by detecting the tracking error signal based on the three-spot method, even if the optical axis of the optical system is slightly missed, the tracking error signal is turned off. An optical pickup apparatus capable of performing accurate tracking sub control by preventing a set from occurring.

Another object of the present invention is to provide an optical pickup apparatus which can simplify the configuration of components of an optical system and further reduce manufacturing costs.

In order to achieve the above object, the present invention, in the light-emitting device, the laser beam is focused on the recording carrier with the optical system interposed therebetween, and the light returned from the recording carrier is interposed with the same optical system. An optical pickup apparatus for condensing on a magnetic field and detecting a tracking error signal and a focus error signal at an output of the light receiving element. It is divided into two by dividing lines which are substantially orthogonal with respect to each other, and a diffraction grating is formed in this one area to separate the subspots in two directions in the three-spot method from the laser beam of the light emitting element, and the other area. The diffraction grating is configured to condense the light returned from the recording carrier onto the light receiving element, respectively.

The light receiving element may be provided in two sets, and the two sets of light receiving elements may be configured to be provided respectively at two positions where primary light of light diffracted by the other region of the diffraction element is collected. . In addition, the other region of the diffractive element may have a blaze characteristic, and a set of light receiving elements may be formed at a position where the primary light having the higher intensity of light is focused.

The other region of the diffraction element may have a structure in which a diffraction grating is formed so that the diffraction direction of light is substantially perpendicular to the track direction.

In addition, the light-receiving element for receiving the light returned from the main spot from the conventional carrier is divided into two elements by the dividing line in the same direction as the dividing line of the region on the diffractive element, and in each region. The addition circuit may include an addition circuit for outputting a sum of the output signals as a reproduction information signal and a subtraction circuit for outputting a difference as a focus error signal.

In addition, the light emitting element and the light receiving element may be housed in the same package, and the window for the cap seal of the package may be configured by the diffraction element.

EXAMPLE

An embodiment of the present invention will be described with reference to FIGS. 1 to 9 as follows.

This embodiment displays an optical pickup device such as a CD player.

As shown in FIG. 1 and FIG. 2, the rotating element 2, the collimating lens 3, and the objective lens 4 are arranged in front of the light emitting element 1 in the optical pickup apparatus. The laser beam A emitted from the light emitting element 1 is guided to the recording surface of the disk 5.

The diffraction element 2 is divided into two regions by a dividing line almost perpendicular to the track direction.

In one region 2a, as shown in FIG. 1 (a), a diffraction grating is formed as if diffraction occurs substantially in the track direction. That is, the + 1st order diffracted light and the -1st order diffracted light of the laser beam A generated in the light emitting element 1 become light beams A1 and A2 forming two subspots in the 3-spot method. It is.

On the other hand, as shown in the other region 2b of the diffractive element 2, a diffraction grating is formed such that diffraction occurs in a direction substantially orthogonal to the track direction.

That is, + 1 of light coming back (B) of the disc (5) -th order diffracted light (B11) and -1st order diffracted light (B ₁₂₎ is, allocated to the two sides room perpendicular to the track direction of the light emitting element (1) It is supposed to be.

Further, in the region (2b) of the other, claim 1 (b) also does not occur to the track direction, the diffraction, as shown in, the + 1st-order diffracted light (B ₁₁₎ and the negative first order diffracted light (B ₁₂ ) Are the main spots formed on the recording surface of the disk 5 and the light beams B ₂₁ , B ₂₂ , B ₂₃ corresponding to the two sub spots, and are focused at positions deflected in the track direction.

However, if the diffraction element 2 is configured as described above, the three beams (A ₃₎ for forming a main spot in the spot method, the laser beam (A) from the light emitting element (1) is of the diffraction element 2 It is formed by the 0th order diffracted light when passing through both regions 2a.2b.

For this reason, for example, when the 0th-order diffraction efficiency of the region 2a is lower than that of the region 2b, the light of the light beam A ₃ forming the main spot, as indicated by the dotted two-dot line in FIG. The intensity distribution is not symmetrical, and there is a fear of causing deterioration of the reproduction signal.

Therefore, both regions 2a. 2b of the diffraction element 2 are set so as to be as smooth as possible with the zeroth order diffraction efficiency.

Further, the dividing line dividing the diffractive element 2 is not an actual line but an imaginary line for dividing the path between the region 2a and the region 2b.

Two photodetectors 6.6 cars are provided on both sides orthogonal to the track direction of the light emitting element 1 on the base on which the light emitting element 1 is provided. The photodetector 6.6 is a position where the + 1st order diffracted light B1 of the returned light B separated by the other region 2b of the diffractive element 2 is focused, and -1st order, respectively. The diffracted light B ₁₂ is arranged at a position to collect. The detection sensitivity is increased by synthesizing the output signals of the photodetector 6.6.

The photodetectors 6.6 are not provided with two as described above, but have blaze characteristics in the other region 2b of the diffraction element 2, for example, + 1st-order diffraction light B ₁₁ . The light intensity may be increased so that sufficient sensitivity can be obtained only by the photodetector 6 provided at one place.

Each of the photodetectors 6 is composed of four light receiving elements 6a-6d arranged in the track direction, as shown in FIG. 5, so that output can be generated individually.

The light receiving elements 6a and 6b are provided adjacent to the boundary in a direction substantially perpendicular to the track direction and in the same direction as the dividing line of the diffractive element 2, so as to form a main spot on the disk 5. The return light B _{33 of} the light beam A3 is to be irradiated on these boundary lines. The light receiving element 6c.6d is provided on both sides of the track direction of the light receiving element 6a.6d, and returns the light B ₂₁ .B _{22 of} the light beam A ₁ .A ₂ forming the subspot. ) Is to be investigated.

Further, the light receiving elements 6a-6b are formed sufficiently long in the direction orthogonal to the track direction so as to cope with fluctuations in the oscillation wavelength of the light emitting element 1 and movement of the light collection point due to assembly error.

The output signals Sa-Sd of the light receiving elements 6a-6d are input to the signal detection circuit shown in FIG. This signal detection circuit is comprised by one addition circuit 7 and two subtraction circuits 8.9.

Then, the output signal Sa. Sb is added by this addition circuit 7 so as to be converted into the reproduction information signal RF. The output signal Sa. Sb is subtracted by the subtraction circuit 8 so as to be converted into the focus error signal RE. Further, the output signal Sc. Sd is subtracted by the subtraction circuit 9 so as to be converted into the tracking error signal TE.

In addition, the light emitting element 1 and the photodetector 6 are integrated into a package 10 as shown in FIG.

The package 10 is again provided with a monitor photodetector 24 for monitoring the issuance strength of the generating element 1 again.

Normally, such a package 10 houses a light emitting element 1, a photodetector 6, and a monitor photodetector 24 therein, as shown in FIG. 9, and a hermetic chamber. Each element is protected from the outside air of moisture or oxygen by sealing by blocking the sealed window 10a.

In this case, the diffraction element 2 is disposed in front of the glass window 10a. However, in the present embodiment, as shown in FIG. 8, the diffraction element 2 is directly fixed to the package 10 instead of the glass window 10a to seal the inside. As a result, the number of parts and the number of assembly labor can be reduced.

The operation of the optical pickup device configured as described above will be described.

The laser beam A generated by the light emitting element 1 first passes through the diffraction element 2. The 0th order diffracted light passing through both regions 2a.2b of the diffractive element 2 is focused on the recording surface of the disk 5 as the light beam A ₃ to form a main spot.

Incidentally, the ± first-order diffracted light generated when the laser beam A passes through one region 2a of the diffractive element 2 is the light beams A ₁ and A _{2 in} two directions, and the disk 5 In the recording surface of the light source, light is collected at front and rear positions along the track direction of the main spot A ₃ to form two sub spots.

Next, the light B ₂₁ -B ₂₃ returned from each recording spot from the recording surface of the disk 5 is diffracted by the other region 2b of the diffractive element 2, and the ± first-order diffracted light Each of these is focused on the photodetector 6.6.

The light B23 of the light beam A3 forming the main spot is irradiated to the light receiving elements 6a.6b of each photodetector 6, and the output signal Sa.Sb is responded to in accordance with the amount of light. ) Is output. These output signals Sa. Sb are added by the addition circuit 7 in the signal detection circuit and output as the reproduction information signal RF.

The returned light B ₂₃ is divided into portions passing through the region 2b of the diffraction element 2 in the light flux of the returned light B, that is, the dividing line of the diffraction element 2. Only the portion on one side of the light beam is diffracted.

Therefore, when the laser beam A focused on the recording surface of the disk 5 is in focus, as shown in FIG. 6 (b), the returned light B ₂₃ receives the light receiving element 6a. 6b. It becomes a point on the edge of the border and collects. In addition, when the focal point of the laser beam A condensed on the recording surface of the disk 5 is out of focus, as shown in Fig. 6 (a) (c), the light receiving element 6a is responded to in the direction in which it is off. Alternatively, a half moon spot is formed in one of the light receiving elements 6b.

Therefore, by the same operation as in the knife edge method, the focus error signal FE is output from the subtraction circuit 8 in which the output signal Sa.Sb is input, thereby detecting the deviation of the focus of the laser beam A. FIG. You can do it.

On the other hand, in the light-receiving element (6c.6d), the light coming back (B _21, B ₂₂₎ of the light beam for forming the sub-spots (A _1, A ₂₎ are respectively irradiated, the output signal (Sc.Sd) is output . Then, with the returning lights B ₂₁ and B ₂₂ , the amounts of light change in opposite directions with the deviation of the tracking based on the three-spot method. Therefore, the tracking error signal TE is output by the subtraction circuit 9 which inputs the output signal Sc.Sd. In order to achieve the same operation as that of the knife age method in detecting the focus error signal FE, in the diffraction element 2, the direction of the dividing line of the two regions 2a. 2b and the photodetector 6 are used. It is necessary to coincide with the direction of the boundary line of the light receiving elements 6a.6b.

In addition, when the oscillation wavelength of the light emitting element 1 changes, the diffraction angle of the light B returned by the diffraction element 2 fluctuates, and the condensing position of the light B returned to the photodetector 6 is changed. In the diffraction direction. In order to prevent the condensing position from diverging in the diffraction direction, it is preferable to match the diffraction direction with the direction of the boundary line of the light receiving elements 6a. 6b.

Therefore, the direction of the dividing line of the area | region 2a.2b in the diffraction element 2, the diffraction direction by the area | region 2b of the diffraction element 2, and the direction of the boundary line of the light receiving element 6a.6b. It is preferable to match with each other.

On the other hand, the interval between two subspots formed on the recording surface of the disk 5 is the tracking error signal TE based on the difference in radius of the music of the track on the inner circumferential side and the track on the outer circumference side of the disk 5. In order to prevent an offset of, it is preferable to make it small.

Further, even when the optical pickup device is attached to the CD player, the interval between the subspots is preferably small in order to prevent a decrease in the detection accuracy of the tracking error signal TE due to an error in the attachment position or the like.

The light receiving elements 6c. 6d need to be arranged on both sides of the track direction of the light receiving elements 6a. 6b at intervals proportional to the interval between the two subspots. Therefore, it is desirable that the interval between the light receiving elements 6c. 6d be small. As described above, the diffraction angle of the light 8 returned by the diffraction element 2 changes due to the change in the oscillation wavelength of the light emitting element 1.

In order to prevent the condensing position of the returned light B from always collapsing from the light receiving elements 6a and 6d, the number of times of the diffraction direction of the light B returned from the light receiving elements 6a.6d is increased. It is desirable to set.

By the way, when the light receiving elements 6a. 6d are arranged as shown in FIG. 7 with respect to the track direction, the distance between the light receiving elements 6c. 6d is reduced and the light receiving elements 6a. It is difficult to make it compatible with setting the frequency | count of the diffraction direction of the light B returned in 6d) large.

Therefore, as shown in FIG. 5, in the diffraction element 2, the diffraction direction of the region 2b is set to be a direction substantially orthogonal to the track direction, so that the region with respect to the diffraction element 2 It is preferable to arrange the light receiving element 6a. 6d on the diffraction direction side of (2b).

In addition, the subspot formed on the recording surface of the disk 5 is preferably close to an elliptical shape having a long axis in the track direction in view of detection sensitivity of the tracking error. Therein, the region 2a of the diffraction element 2 in which the light beam A ₁ .A ₂ forming the subspot is separated from the laser beam A has a short number of times, for example, in the track direction, and is diffracted. It is desirable that the number of gratings is small.

Therefore, in the same point as above, it is preferable to divide the region 2a.2b in the diffraction element 2 by a dividing line in a direction substantially orthogonal to the track direction, whereby the light emitting element 1 Despite the change in the oscillation wavelength, the track Kim error signal (TE), etc., which does not include an offset, can be detected with high accuracy and high accuracy. Can be reduced.

As described above, the optical pickup apparatus according to the present invention condenses the laser beam emitted from the light emitting element on the recording carrier with the wide angle system interposed therebetween, and returns the light returned from the recording carrier through the same optical system. An optical pickup apparatus for condensing light and detecting a tracking error signal and a focus error signal at an output of the light receiving element, wherein a diffraction element is disposed in front of the light emitting element and the light receiving element, and the area on the diffraction element is located in the track direction. The dividing line is divided into two by substantially orthogonal dividing lines, and a diffraction grating is formed in this one region to separate the subspots in two directions in the three-spot method from the laser beam of the light emitting element, and the other region. The diffraction grating is configured to condense the returning light from the recording carrier onto the light receiving element, respectively.

The light-receiving elements are provided in two sets, and these two sets of light-receiving elements are respectively provided at two positions where primary light of light diffracted by the other region of the diffraction element is collected. It may be good.

In addition, the other region of the diffraction element may have a blaze characteristic, and a set of light receiving elements may be provided at a position where the primary light of the higher light intensity is focused.

The other region of the diffractive element may have a structure in which a diffraction grating is formed so that the diffraction direction of light is substantially perpendicular to the track direction.

In addition, the light receiving element for receiving the light returned from the main spot from the recording carrier is divided into two elements by the dividing line in the same direction as the dividing line of the region on the diffractive element, and in each region. It may be configured to include an addition circuit for outputting the output signal as a reproduction information signal and a subtraction circuit for outputting a difference as a focus error signal.

In addition, the light emitting element and the light receiving element may be housed in the same package, and the window for the cap seal of the package may be configured by the diffraction element. As a result, the focus error signal can be detected based on a kind of knife edge method as in the prior art, while the tracking error signal can be detected based on a highly reliable three-spot method. This eliminates the occurrence of an offset in the tracking error signal.

Therefore, by using the diffractive element as in the prior art, accurate tracking servo control can be performed while reducing the number of parts of the optical system.

In addition, if the light emitting element and the light receiving element are integrated and housed in a body, and the diffraction element is used as the window for cap cap, the manufacturing cost can be further reduced.

Claims (6)

The optical pickup device condenses the laser beam generated by the light emitting element on the recording carrier with the optical system interposed therebetween, and collects the light returned from the recording carrier on the light receiving element with the same optical system therebetween. In an optical pickup apparatus for detecting a tracking error signal and a focus error signal, a diffraction element is disposed in front of the light emitting element and the light receiving element, and the area on the diffraction element is divided into two by a dividing line which is substantially orthogonal to the track direction. A diffraction grating is formed in one region to separate the subspots in two directions in the three-spot method from the laser beam of the light emitting element, and the light returned from the recording carrier is condensed on the light receiving element in the other region. An optical pickup device having a configuration in which a diffraction grating is formed. In the optical pickup apparatus of claim 1, two sets of light receiving elements are provided, and two sets of light receiving elements are respectively located at two positions where primary light of the returned light diffracted by the other region of the diffraction element is collected. Optical pickup device made up of the installed configuration. The optical pickup apparatus of claim 1, wherein the optical pickup apparatus has a blaze characteristic on the other region of the diffraction element and is provided at a position where a set of light receiving elements is focused at a position where primary light of the higher light intensity is collected. . The optical pickup apparatus of claim 1, wherein the other region of the diffraction element is formed such that a diffraction grating is formed such that the diffraction direction of light is substantially perpendicular to the track direction. The optical pickup apparatus of claim 1, wherein the light receiving element that receives the light returned from the main spot from the recording carrier is divided into two elements by the dividing line in the same direction as the dividing line of the region on the diffractive element. And an addition circuit for outputting the signal of each signal output in each area as a reproduction information signal, and a subtraction circuit for outputting a difference as a focus error signal. An optical pickup apparatus according to claim 1, wherein the light emitting element and the light receiving element are housed in the same package and the window for cap seal of the package is constituted by a diffraction element.

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